Means for influencing the variations of magnetic fields.



F. G. LILJENROTH. v MEANS FOR INFLUENCING THE VARIATIONS 0F MAGNETIC FIELDS.

' APPLICATION FILED IEIBJG, 1912.

1,100,895, Patented June 23, 1914.

runs G. Lmsnaorn, or vns'rnnAs, SWEDEN.

MEANS FOR INFLUENCING THE VABiATIONS @F MAGNETIC FIELDS.

Specification of Letters Patent.

Patented June 23, 1914.

Application filed February 15, 1912. Serial No. 677,658.

To all whom it may concern:

Be it known that I, FRANs G. LILJEN- ROTH, a citizen of the Kingdom of Sweden residing at Vesteras, Sweden, have invente new and useful Improved Means for Influencing the Variations of Magnetic Fields, of which the following is aspecification.

When the strength of a magnetic field is varied there arises, as is well known in an electric circuit inductively connected with the field, an electromotive force which is proportional to the variation of the field per unit of time and is so directed that it counteracts the variation of the field. On account thereof, a magnetic field requires, as is well known, a certain period of time to be created or to disappear or generally to be varied as to its strength. In electric machines, especially large alternating current generators and continuous current generators for supplying reversible motors according to the Ward-Leonard system-said circumstance is connected with several inconveniences. In reversible continuous current motors for instance for driving rolling mills it is desirable to efiect speedy variations oi the number of revolutions and speedy reversions, which requires that the voltage and accordingly the field strength of the continu ous current generator should be varied al most instantaneously. On the other hand there results in large alternating current generators during short circuits, a momentary rush of current for the reason that the field does not disappear rapidly enough, and on the other hand a too long period of time is required to vary the field current, on account whereof, it is diflicult to maintain a constant voltage when the load is varied.

The object of the arrangement described" herebelow' is generally to efiect a more rapid variation of a magnetic field than that which is reached by means of the arrangements' heretofore used. On account thereof it is possible in electric machines and appal ratus to reach a more rapid regulation of the I voltage than otherwise and a reduction of; the rush of current in short circuits and connecting' operations. The invention consists chiefly in the pro- 1 vision in the magnetic field to be varied of a winding in which is induced fa current which is dependent on the v ariation of the field per unit of time and which is usedto deliver'the excitation energy or a part thereof to one or more dynamo electric machines,

K win ing which are directly or indirectly connected to circuits in magnetic connection with the field to be varied.

In the accompanying drawings, I have shown some embodiments of my invention.

Figures 1 1 and 2 to 7, show diagrammatically each one form of the invention.

Referring to Fig. l G represents the armature of a continuous current generator supplying translating devices T and havm a main field winding L The said main fie d winding L is supplied with current from a continuous current machine M hav ing an excitation winding f supplied from a separate source of current M A resistance B may be provided in the circuit of the winding L or a resistance B, may be provided in the circuit of the winding 1 for the purpose of regulating the voltage of the generator G by varying the strength of its eld. L indicates an auxiliary field winding disposed on the stationary magnetic core of the generator G in inductive relation to the magnetic field-created by the main field Winding L The winding L is connected to an auxiliary field winding f, of the continuous current machine M. As long as the magnetic flux of the field of the generator G remains constant, the auxiliary windings L and f, are currentless. When, however, the said magnetic flux is subjected to variations, for instance on account of an adjusting of the regulating resistance R or on account of variations of the load on the circuit supplied from the generator G, an E. induced in the windings L and L said E. M. F. being proportional to the variation of the magnetic flux per unit of time. The current proportional thereto generated in the circuit of the windin s L and f, causes a temporary variation 0% the magnetination 0 the exciter M which results in a variation (increase or decrease) of the voltage of said exciter, which practically like- M. F. is

ator It may be assumed that the wind-f is so connected up in relation to the L and the winding f that the said variation of voltage between the terminals ofithe enciter M caused by. the current supplied by' the winding L is directed oppositel, to the voltage induced in the main fiel winding L, on account of the variation the magnetic field of the "generator G. The addit onal yoltage momentaril sup- 100 wise is proportional to the variation per unit ranged ,in ig. 1.. The exciter M supalyin 'fieldwinding L has a. field win celerate the variation of the field of the nerator G. By suitable choice of the num- 2. of turns of the windin L, and the ratio of transformation of t e continuous current machine M the-said additional voltage of the exciter M and the voltage induced in the main field winding L on account of the variation of the magnetic field of the generator G may be brought to nullify each other, which results in that the stren th of the magnetic field of the generator may be varied almost instantaneously from one value to another.

In Fig. 1" I have shown a modification of the invention applied to a polyphase alternating current generator supplying current to a polyp ase induction motor L is the main field winding of the generator" G and L, an auxiliary field winding arsubstantially in the same manner has e ing connected'in shunt to its own armature. The auxiliaryfield winding] of the exciter M is connected in series with the auxiliary field winding L,. If, for instance, the load on the induction motor I is carried this generally results in a variation of the intensity as well as the lag of the current supplied from the generator G to the motor I, and this variation in its turn causes, on account of the armature reaction, a variation the auxilia of the magnetic flux of the generator G. A momentary current is, accordingly, induced in the circuits of the windings L, and f, causing an additional excitation of the machine M which in its turn delivers an increased magnetizing current to the main field winding L thereby accelerating the variation of the magnetic flux of the generator G.

The arrangement may also be carried out in such manner that the auxiliary winding L, of the generator G is connected in series with the field winding f of the exciter M such an arrangement being shown in Fig. 2. The windin f of the exciter M is as in Fig. 1 sup lie from a separate source of current M, ut, if desired, it may be shunted .to the terminals of the machine M as in Fig. 3

1. This arrangement works substantial in the same manner as that shown in Fig. 1'.

In the form shown in Fig. 3 an auxiliary exciter M is connected in series with the exciter M and the main field winding L of the generator G. The field winding 1, of the machine M is connected in series with field winding L, of the generator G. en the magnetic flux of the generator G for some reason is varied, the

---winding f, consequently will receive a mo- I'nentary exciting current which .is proportional to the variation 0 practically the magnetic tin: of the generator G .per unit of time. On account thereof there iscreated between the terminals of the machine M, a voltage that will wholly or partl' nullify the voltage induced in the windin 1 on account of the variation of the sai magnetic The form shown in Fig. 4 differs from that shown in Fig. 3 only in that the field winding 1, of the machine M is not connected directly to the auxiliary field windin L, of the generator G but to the termina s of a continuous current machine'M, the field windin f, of which is connected to the auxiliary fie d windin L,. This arrange ment works substantia y in the same manner as that shown in Fig. 3.

In the form shown in Fig. 5 a continuous current machine M is connected in series" with the field winding 7 of the machine M iliary continuous current machine M,, Fi

5, res ectivel M,, Fi 4, one may rovi c said r achine besides v vith the field v inding f, respectivelyj, connected to the auxiliary field winding L, of the generator G with a second field winding, for instance connected in shunt to the terminals of the machine and having such a lar e resistance that the machine cannot excite itself unless the wind-' ing L, delivers a supplementary magnetizmg current in the one direction or the other. Fig. 7, shows such a shunt connected field winding f, applied to an arrangement according to Fig. 5, but it ma be understood that such a winding f, may provided also in the machine M in the forms shown in Figs. 3 and 6 or in the machine M,, Fig. 4.

For the action aimed at of the above described arran ement it is necessa that the reaction of t e auxiliary field winding L, on the field of the generator G be small, that the time-constants of the continuous current machines are small in relation to those of the main circuit, and that the conwinding L, act in opposite direction to that i supposed above, it is possible in all forms of the invention described above to retard the variations ofthe strength of the field of the generator G.

I claim:

1. In an electric apparatus, a main field for creating a magnetic field, an

arrangement of said magnetic field, consisting of an auxiliary winding disposed in inductive relation to said main field winding, and means for supplying to the said main field winding a magnetizing effect dependent on the current induced in the auxiliary winding, substantially as and for the purpose set forth.

2. In a dynamoelectric machine a main field winding adapted to be separately excited, an arrangement-for accelerating the variations of the magnetic field of the machine, consisting of an auxiliary field winding disposed in inductive relation to said main field winding, and means for increasing the magnetizing efiect supplied to the main field Winding dependent on the current induced in the auxiliary winding, substantially as and for the purpose set forth.

3. In an electric apparatus, a main field winding for creating a magnetic field, an arrangement for influencing the variations of said magnetic field, consisting of an auxiliary field winding disposed in inductive relation to said main field winding, and a continuous current machine the armature of which is connected to said main field winding and adapted to supply a magnetizing efiect to said main field winding dependent on the current induced in said auxiliary field winding, substantially as and for the purpose set forth.

4. In a dynamo-electric machine, a main field winding, an arrangement for accelerating the variations of the magnetic field of the machine, consisting of an auxiliary field winding disposed in inductive relation to said main field winding, and a continuous current machine the armature of which is connected to said main winding, and adapt ed to supply a magnetizing efiec't to said main field winding dependent on the current induced in said auxiliary field winding, substantially as and for the purpose set forth.

5. In a dynamo-electric machine, a main field winding, an arrangement for influencing the variations of the magnetic field of the machine, consisting of an auxiliary field winding disposed in inductive relation to said main field winding, a continuous current machine connected to said main winding and having a field winding supplied with a magnetizing current dependent on the current induced in said auxiliary winding on variations of the strength of the magnetic field of the dynamo-electric machine, substantially as and for the purpose set forth.

6. The combinatiflion' with a dynamo-electric machine having a main field winding and an auxiliary field winding, of an exciter for supplying magnetizing effect dependent on the current induced in said auxiliary field winding on variations of the magnetic flux of the dynamo-electric machine, substantially as and for the purpose set forth.

to said main field winding a 7 The combination with a dynamo-electric machine having a main field winding and an auxiliary j ield winding, of a continuous current machine having a field winding supplied with a magnetizing current dependent on the current induced in said auxiliary winding gnyariations of the magnetic flux of the dynamo electric machine and an armature connected in series with said main field winding, substantially as and for the purpose set forth.

8. The combination with a dynamo-electric machine having main field windings and auxiliary field windings, armature circuit {,of which is connected to said main field windings, and an auxiliary exciter having an armature connected to the of an exciter the field winding of the first mentioned exciter,

and a field winding connected to said auxiliary windings, substantially as and for the purpose set forth.

In testimony that I claim the foregoing as my invention, I have signed my name in presence of two subscribin witnesses.

FRANS G. LIL ENROTH. Witnesses:

CONRAD DELMAR, JOHN DELMAR. 

